1. Field
An example of this invention relates to a disk device having a disk for use as a recording medium.
2. Description of the Related Art
In recent years, disk devices, such as magnetic disk devices, optical disk devices, etc., have been widely used as external recording devices of computers or image or music recording/reproducing apparatuses.
For example, a magnetic disk device generally comprises a magnetic disk, spindle motor, head actuator, voice coil motor, circuit board unit, etc., which are arranged in a case. The spindle motor supports and rotates the magnetic disk. The head actuator supports magnetic heads and the voice coil motor drives the head actuator. The head actuator is provided with a bearing portion attached to the case and arms that are stacked on the bearing portion and extend from the bearing portion. A magnetic head is mounted on each arm by means of a suspension.
According to a device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-5783, for example, a case is composed of an open-topped base on which mechanical sections are mounted and a top cover that covers an opening of the base. Normally, the top cover is fastened to the peripheral edge portion of the upper surface of the base with screws. In order to enhance the rigidity of the top cover, it is provided with a drawn portion, e.g., a circular arcuate depression. Further, a nameplate label that indicates the model number, manufacturer, etc. of the magnetic disk device is pasted on a surface of the top cover. The label is stuck to the top cover surface so as to conceal the whole depression.
The magnetic disk device constructed in this manner undergoes vibration that is caused by rotations of the spindle motor and the magnetic disk, vibration of the head actuator attributable to a windage that is caused by the rotation of the magnetic disk, vibration that is caused by a seek action of the head actuator, etc. The vibrations of the spindle motor and the head actuator, which behave as vibration generating portions, are transmitted to the plate-shaped top cover through the base and a pivot or the like of the head actuator. Thereupon, the top cover vibrates and generates noise. If the frequency of normal mode of vibration of the cover is approximate to a frequency transmitted to the top cover, in particular, resonance is developed, so that the vibration amplitudes of the spindle motor and the head actuator increase. In consequence, noises also increase inevitably.
In the case where the nameplate label covers the whole surface of the drawn portion of the top cover, the vibration of the top cover is transmitted to the nameplate label by air propagation and solid propagation, whereupon the label vibrates. The vibration of the label is transmitted again to the top cover by air propagation, so that the vibration of the top cover is excited inevitably. Owing to this phenomenon, the magnitude of the vibration of the top cover increases, so that the level of the noise from the top cover is raised. If a vibration damper is stuck to the drawn portion in order to suppress the vibration of the top cover to reduce the noise, the number of parts increases, resulting in an increase in cost.
Modern magnetic disk devices that are used in a wide variety of fields require reduction of noises.